netdev - Re: KS8695: possible NAPI issue

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Date:	Wed, 3 Mar 2010 09:28:12 +0100
From:	Yegor Yefremov <yegorslists@...glemail.com>
To:	Dick Hollenbeck <dick@...tplc.com>
Cc:	figo zhang <figo1802@...il.com>, netdev@...r.kernel.org,
	zealcook@...il.com
Subject: Re: KS8695: possible NAPI issue

>>>> I'm using 2.6.33 kernel and I noticed such a strange behavior:
>>>>
>>>> after system start I transfer one file via netcat from my development
>>>> host, after this transfer the network is not functioning i.e. no pings
>>>> possible etc.
>>>>
>>>> To narrow down the problem I checked out this commit
>>>>
>>>>
>>>> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=451f14439847db302e5104c44458b2dbb4b1829d.
>>>> Till here the network driver is functioning as intended, but after
>>>> NAPI introduction I have this issue. With latest git-pull of "Linus'
>>>> kernel tree" I can't even ping right after the systems start.
>>>>
>>>> Any Ideas? What am I missing?
>>>>
>>>>
>>>
>>> No idea, although I am using the same ARM chip, my kernel is at 2.6.30.5,
>>> and except for this occasional loss of connection I get, the ethernet
>>> driver
>>> seems to work better than what you are reporting.
>>>
>>
>> from linux-2.6.32, this ethernet  driver have add NAPI support, would
>> you like to
>> try using this version?
>>
>
> Seems like a lot of work for me, given that my 2.6.30.5 kernel is mostly
> working.   Yegor is having the problems on the newer kernels, newer than
> mine.  Sounds like a warning flag to me, not an incentive.
>
> What is NAPI and why do I care?

Here is Wikipedia article: http://en.wikipedia.org/wiki/NAPI

The problem also is that I really need a kernel version not less than
2.6.33 because of the support of other platforms.

I sniffed a little with wireshark and the symptoms are the following:

after netcat transfer the system sends only ARP requests and no other packets.

I just git-pulled the latest Linus tree and the network still has the
above described issues.

Figo, could you test the latest kernel with netcat transfers? So you
could reproduce this behavior?

Yegor
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